671981 has 2 divisors, whose sum is σ = 671982. Its totient is φ = 671980.

The previous prime is 671971. The next prime is 671999. The reversal of 671981 is 189176.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 538756 + 133225 = 734^2 + 365^2 .

It is a cyclic number.

It is not a de Polignac number, because 671981 - 2⁶ = 671917 is a prime.

It is a super-2 number, since 2×671981² = 903116928722, which contains 22 as substring.

It is a Sophie Germain prime.

It is a Chen prime.

It is a Curzon number.

It is a congruent number.

It is an inconsummate number, since it does not exist a number n which divided by its sum of digits gives 671981.

It is not a weakly prime, because it can be changed into another prime (671911) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 335990 + 335991.

It is an arithmetic number, because the mean of its divisors is an integer number (335991).

2⁶⁷¹⁹⁸¹ is an apocalyptic number.

It is an amenable number.

671981 is a deficient number, since it is larger than the sum of its proper divisors (1).

671981 is an equidigital number, since it uses as much as digits as its factorization.

671981 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 3024, while the sum is 32.

The square root of 671981 is about 819.7444723815. The cubic root of 671981 is about 87.5895572854.

It can be divided in two parts, 67 and 1981, that added together give a 11-th power (2048 = 2¹¹).

The spelling of 671981 in words is "six hundred seventy-one thousand, nine hundred eighty-one".